Short-Term Preconditioning With Blood Flow Restricted Exercise Preserves Quadriceps Muscle Endurance in Patients After Anterior Cruciate Ligament Reconstruction.

Tina Žargi,Klemen Stražar,Matej Drobnič,Alan Kacin

doi:10.3389/fphys.2018.01150

Abstract

Surgical ACL reconstruction performed with a tourniquet induces compression and ischemic stress of the quadriceps femoris (QF) muscle which can accelerate postoperative weakness. Given that low-load blood flow restricted (BFR) exercise is potent in enhancing muscle oxygenation and vascular function, we hypothesized that short-term preconditioning with low-load BFR exercise can attenuate QF muscle endurance deterioration in the postoperative period. Twenty subjects undergoing arthroscopic ACL reconstruction performed 5 exercise sessions in the last 8 days prior to surgery. They were assigned into either BFR group, performing low-load BFR knee-extension exercise, or SHAM-BFR group, replicating equal training volume with sham occlusion. Blood flow (near-infrared spectroscopy) and surface EMG of QF muscle during sustained isometric contraction at 30% of maximal voluntary isometric contraction (MVIC) torque performed to volitional failure were measured prior to the intervention and again 4 and 12 weeks after surgery. There was an overall decrease (p = 0.033) in MVIC torque over time, however, no significant time-group interaction was found. The time of sustained QF contraction shortened (p = 0.002) in SHAM-BFR group by 97 ± 85 s at week 4 and returned to preoperative values at week 12. No change in the time of sustained contraction was detected in BFR group at any time point after surgery. RMS EMG amplitude increased (p = 0.009) by 54 ± 58% at week 4 after surgery in BFR group only. BFm increased (p = 0.004) by 52 ± 47% in BFR group, and decreased (p = 0.023) by 32 ± 19% in SHAM-BFR group at week 4 after surgery. Multivariate regression models of postoperative changes in time of sustained QF contraction revealed its high correlation (R2 = 0.838; p < 0.001) with changes in BFm and RMS EMG in the SHAM-BFR group, whereas no such association was found in the BFR group. In conclusion, enhanced endurance of QF muscle was triggered by combination of augmented muscle fiber recruitment and enhanced muscle perfusion. The latter alludes to a preserving effect of preconditioning with BFR exercise on density and function of QF muscle microcirculation within the first 4 weeks after ACL reconstruction.

Highlights

Quadriceps femoris (QF) muscle weakness is the major cause of poor functional status of patients following otherwise successful anterior cruciate ligament (ACL) reconstruction (Lindstrom et al, 2013; Thomas et al, 2015)
There were no significant differences in body mass index (BFR = 24.3 ± 3.9 kg · m−2; SHAM-blood flow restricted (BFR) = 23.9 ± 2.9 kg · m−2), age (BFR = ± 6 years; SHAM-BFR = ± 5 years) and Lysholm composite score (BFR = 78 ± 11; SHAM-BFR = 76 ± 16) between the groups
For SHAMBFR group, the correlation between time of contraction and Root mean square (RMS) EMG was high (r = 0.701; r2 = 0.491) and. This is the first evidence of preventative effect of lowload BFR exercise on skeletal muscle endurance following ACL reconstruction

Summary

Introduction

Quadriceps femoris (QF) muscle weakness is the major cause of poor functional status of patients following otherwise successful anterior cruciate ligament (ACL) reconstruction (Lindstrom et al, 2013; Thomas et al, 2015). Rather low efficiency of standard postoperative rehabilitation has diverted the focus of clinical research in recent years toward the so-called preconditioning, or prehabilitation, exercise programs. They aim to increase lower limb muscle strength prior to surgery, which is believed to substantially attenuate the deterioration of muscle function in the aftermath. Temporary enhancements of muscle strength and function can be clearly gained with various preconditioning programs (Keays et al, 2006; Hartigan et al, 2009), there is little evidence to support their alleged protective effect against muscle deconditioning in the postoperative period (Shaarani et al, 2013; Kim et al, 2015). Enhancing preoperative QF muscle endurance may be more important for effective protection against postoperative deconditioning in these patients

Methods

Results

Conclusion